Inhalation or respiratory systems for administering respirable gas to an individual are well known. Of particular significance are apparatus employed in the medical and dental arts for dispensing medical and dental gases, such as anesthetic and analgesic gases and oxygen and nitrous oxide, to a patient.
Typically, inhalation systems include a source of a selected pressurized gas and means to deliver the gas to the external respiratory organs of the patient. A breathing device, such as a mask, is fitted to the face of the patient to embrace the nose and/or the mouth. The source, which may be either portable or fixed, usually includes a flow regulator. A delivery conduit, generally in the form of a flexible hose, communicates between the source and the breathing device. Optionally, the system may include scavenging apparatus comprising a return conduit extending from the breathing device to a source of vacuum.
The prior art has devised an array of personal breathing devices in numerous structural configurations. These personal breathing devices, commonly referred to as inhalation masks or facemasks, serve a variety of functions. Known, for example, are masks that extend over the mouth and the nose of the patient while others receive only the nose. Commonly, masks include a fitting for attachment of a gas delivery conduit. In some instances, an exhalation valve is incorporated into the mask to prevent the entrance of ambient air.
In recognition of the concern over collection and disposal of expired gas, skilled artisans have developed a variety of solutions useful with inhalation masks, such as scavenger valve attachments, scavenger hoods useful with inhalation masks, and scavenger circuits. Although these prior art examples initially appeared adequate, structural complexities inherent in the prior art scavenging solutions have proven less than satisfactory, thereby necessitating continued improvement in the art.